Cyber-attacks traced to China targeted at least 48 chemical and military-related companies over the summer in an effort to steal technical secrets, an American computer security company has said, raising the temperature of complaints about pervasive internet crime emanating from the new superpower..

The targets included 29 chemical companies and 19 others which make advanced materials used by the military, said security firm Symantec in a report. It said the group included multiple Fortune 100 companies but did not identify them or say where they were located.

“The purpose of the attacks appears to be industrial espionage, collecting intellectual property for competitive advantage,” said the report.

The claim comes as a conference meets in London to discusscybercrime and internet attacks, led by the defence secretary William Hague, and after the chief of the GCHQ listening agency warned that threats against government infrastructure from foreign hackers were at “disturbing” levels.